THE ANGIOSPERMAE 1407 



name has been chosen to avoid confusion with what was previously known 

 as the " LiHum type ", i.e., the Adoxa type. The condition in Lilium and 

 FritiUaria is, in fact, more complex. Four megaspore nuclei are formed in 

 the sporogenous cell and these arrange themselves with three at the anti- 

 podal end and one at the micropylar end of the cell. The latter divides 

 normally into two, but during division of the other three their groups of 

 chromosomes are intermingled before separating, so that two triploid 

 nuclei result. This provides a second four-nucleate stage, but very different 

 from the first. All four nuclei now divide again to produce eight, four 

 micropylar nuclei which are haploid and four antipodal nuclei which are 

 triploid. The eight nuclei take up the normal arrangement and the two polar 

 nuclei fuse to produce a tetraploid nucleus. 



Finally, therefore, there are three haploid nuclei which form the oosphere 

 and synergidae, three triploid nuclei which form the antipodals and one 

 tetraploid polar nucleus. The latter after fertilization by a male gamete 

 nucleus is naturally pentaploid and so are all the endosperm nuclei formed 

 from it subsequently. 



This curious type seems to be general throughout the Lilioideae and 

 has been found in a number of other, quite unrelated genera, e.g., Piper, 

 Cornus, Armeria, Statice and Gaillardia. 



6. Tetrasporic, eight-nucleate sacs. The Plumbago type. The four 

 megaspore nuclei arrange themselves with one at each end of the cell and 

 one at each side. They divide to make eight, arranged in pairs. One of the 

 micropylar nuclei is cut off by a membrane and forms the oosphere. There 

 are no synergidae. The other micropylar nucleus and one from each of the 

 remaining pairs move to the centre of the sac and form a group of four 

 polar nuclei which may fuse. The three remaining nuclei frequently dis- 

 appear but they too may be cut off by membranes and give the appearance 

 of accessory oospheres, one at the antipodal end and one at each side of the 

 sac. This type is only known in the Plumbaginaceae. 



7. Tetrasporic, four-nucleate sacs. The Plumhagella type. This resembles 

 the FritiUaria type, but ends at the secondary four-nucleate stage. The 

 four megaspore nuclei are arrayed as in FritiUaria. The three chalazal 

 nuclei then fuse, giving a secondary two-nucleate stage. A further division 

 yields two haploid and two triploid nuclei. One haploid nucleus forms the 

 oosphere, with no synergidae; one triploid nucleus forms a single anti- 

 podal cell and the two others fuse to form a single tetraploid polar nucleus. 



This type is known from only one species, Plumbagella micrantha, 

 closely related to Plumbago, but it shows certain resemblances both to the 

 FritiUaria and to the Plumbago types. 



8. Tetrasporic, sixteen-nucleate sacs. The Drusa type. This type is 

 characterized by the multiplication of antipodals. The four megaspore 

 nuclei arrange themselves with one at the micropylar end and three at the 

 chalazal end of the sac. This is followed by two successive phases of 

 division, giving four micropylar nuclei and twelve antipodals. From each 

 group one nucleus migrates to the centre to form the polar pair. Thus the 



